Predominant period and equivalent viscous damping ratio identification for a full-scale building shake table test

2017 ◽  
Vol 46 (14) ◽  
pp. 2459-2477 ◽  
Author(s):  
Michelle C. Chen ◽  
Rodrigo Astroza ◽  
José I. Restrepo ◽  
Joel P. Conte ◽  
Tara Hutchinson ◽  
...  
Keyword(s):  
Damping Ratio ◽  
Full Scale ◽  
Shake Table Test ◽  
Viscous Damping ◽  
Shake Table ◽  
Equivalent Viscous Damping ◽  
Predominant Period ◽  
Equivalent Viscous Damping Ratio

scholarly journals Study on the Aging Time Variation Law of Mechanical Properties of the Laminated Rubber Bearing in Coastal Bridges considering Frictional Slip

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yue Li ◽  
Chongming Gao ◽  
Chong Li ◽  
Qian Li
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Damping Ratio ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Coastal Bridges ◽  
Shape Coefficient ◽  
Rubber Bearings ◽  
Frictional Slip ◽  
Equivalent Viscous Damping Ratio

As an important support member in the structural system of coastal bridges, the frictional slip and the rubber aging of laminated rubber bearings will affect the service safety of the overall structure in earthquakes. In order to investigate the mechanical properties aging law of the rubber bearings considering frictional slip in the coastal bridges, a frictional slip experiment was carried out on the laminated rubber bearings. Moreover, the influence of rubber aging on the mechanical properties of the bearings with various shape coefficients was analyzed by the finite element method during the 100 years of service life of bridges. The results indicate that (1) the horizontal and vertical stiffness of the bearing increase linearly with the aging time of the rubber. The amplification of the bearing stiffness also grows with the shape coefficient of the bearing. (2) The frictional slip initiation displacement of the bearing grows with the rubber aging time. Furthermore, the larger the shape coefficient of the bearing is, the more the frictional slip initiation displacement of the bearing increases. (3) With the increase of the aging time, the equivalent viscous damping ratio of the bearing continues to increase and more energy is consumed by frictional slip. For the bearing with the shape coefficient of 16.38, the equivalent viscous damping ratio at 100 years of rubber aging time is 1.17 times higher than that of the initial state of the bearing, and 33.21% more energy is consumed through frictional slip. Given that the marine environment accelerates rubber aging and changes the mechanical properties, the effects of the frictional slip and rubber aging properties of the laminated rubber bearings on the seismic dynamic response of bridges should be considered in the seismic design of coastal bridges.

Viscoelastic Damping of Ortho-Planar Springs

2008 ◽  
Author(s):  
Sterling Anderson ◽  
Brian D. Jensen
Keyword(s):  
Damping Ratio ◽  
Spring Constant ◽  
Viscoelastic Damping ◽  
Viscous Damping ◽  
Constrained Layer Damping ◽  
Equivalent Viscous Damping ◽  
Background Theory ◽  
Modal Damping ◽  
Damping Treatments ◽  
Equivalent Viscous Damping Ratio

This paper presents the design of a damped ortho-planar spring that uses viscoelastic constrained-layer damping to reduce the free response oscillations of the spring and suppress modal resonances in that response. Background, theory, and applications surrounding fully-compliant ortho-planar springs and viscoelastic damping treatments are first discussed. Next, the effect of various constrained layer thickness on the spring constant, damping ratio, equivalent viscous damping ratio, modal frequencies, and modal damping ratios are compared, and trends discussed. The results show that the equivalent viscous damping co-efficient of the viscoelastically-damped spring can be increased to nearly 2.5 times that of the reference configuration without significantly changing the size of the constraining layer or the spring constant of the ortho-planar spring. Viscoelastically-damped ortho-planar springs are also shown to successfully remove mechanical noise from a contact resistance test stand.

Quality Factors of Rotors With Hydrodynamic Bearings

1993 ◽  
Vol 115 (2) ◽  
pp. 261-265 ◽  
Author(s):  
J. S. Rao
Keyword(s):  
Quality Factor ◽  
Damping Ratio ◽  
Maximum Amplitude ◽  
Viscous Damping ◽  
Quality Factors ◽  
Equivalent Viscous Damping ◽  
Hydrodynamic Bearings ◽  
At Resonance ◽  
Equivalent Viscous Damping Ratio ◽  
Undamped Natural Frequency

The quality factor of a system is a measure of the maximum amplitude of vibration that occurs at resonance when the frequency of excitation is equal to the undamped natural frequency. This factor can be easily determined for a given mode of vibration, given its equivalent viscous damping ratio, as Q = 1/2ξ. Such a definition becomes complicated for a rotor mounted on hydrodynamic bearings. This note discusses some factors involved in estimating the quality factor of a rotor.

Equivalent Viscous Damping Ratio of Steam Turbine Foundation in Nuclear Power Plants

2011 ◽  
Vol 148-149 ◽  
pp. 1113-1117
Author(s):  
Xiang Yang Zhou
Keyword(s):  
Steam Turbine ◽  
Concrete Structure ◽  
Stiffness Matrix ◽  
Composite Structures ◽  
Power Plants ◽  
Damping Ratio ◽  
Viscous Damping ◽  
Vibration Isolator ◽  
Equivalent Viscous Damping ◽  
Equivalent Viscous Damping Ratio

According to the complex damping theory, the formula to calculate equivalent damping ratio of composite structures is derived from damping stiffness matrix by dynamic analysis. The finite element model of a steam turbine foundation is established. The equivalent viscous damping ratio is calculated from natural frequencies, modes and structural stiffness matrix. Due to the vertical stiffness of spring vibration isolator is larger than lateral stiffness of concrete structure, most of free vibration modes of the foundation are movements of concrete structure. Therefore, the equivalent mode damping ratio is close to the one of concrete structure. The dynamic response is overestimated, if the equivalent mode damping ratio is derived from the average of spring vibration isolator and concrete structural ones.

scholarly journals Design and Experimental Study on Shock-Absorbing Steel Bar with Limit Function for Bridges

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Zhaoguang Li ◽  
Ri Gao ◽  
Wei Jia
Keyword(s):  
Energy Dissipation ◽  
Damping Ratio ◽  
Hysteresis Curve ◽  
Limit Function ◽  
Viscous Damping ◽  
Initial Stiffness ◽  
Equivalent Viscous Damping ◽  
Steel Bar ◽  
Steel Bars ◽  
Equivalent Viscous Damping Ratio

The existing research on shock-absorbing steel bars is only limited to simply supported beam bridge. In order to expand the application of shock-absorbing steel bars to other fields, this paper develops a novel shock-absorbing steel bar with limit function, and it is suitable for continuous beam bridges. The structure and working mechanism of the shock-absorbing steel bar are analyzed. Three sets of specimens of the shock-absorbing steel bar are fabricated and then repeatedly loaded by the designed quasistatic loading device, in order to investigate their seismic performance parameters, including hysteresis curve, skeleton curve, and initial stiffness and equivalent viscous damping ratio. The results show that when the displacement of the specimen exceeds the initial gap, it enters the stage of energy dissipation and has a stable hysteresis curve and good fatigue resistance. Besides, the shock-absorbing device has a high initial stiffness and can provide stable bearing capacity after yielding. The equivalent viscous damping ratio reflects that the designed shock-absorbing steel bar has good energy dissipation capacity.

scholarly journals Energy-Based Design Criterion of Dissipative Bracing Systems for Seismic Retrofit of Frame Structures

2018 ◽  
Author(s):  
Gloria Terenzi
Keyword(s):  
Damping Ratio ◽  
Dissipative System ◽  
Design Criterion ◽  
Frame Structures ◽  
Element Analysis ◽  
Equivalent Viscous Damping ◽  
Linear Behaviour ◽  
Energy Based Design ◽  
Equivalent Viscous Damping Ratio ◽  
Reduction Factors

Direct sizing criteria represent useful tools in the design of dissipative bracing systems for the advanced seismic protection of existing frame structures, especially when incorporated dampers feature a markedly non-linear behaviour. An energy-based procedure is proposed herein to this aim, focusing attention on systems including fluid viscous devices. The procedure starts by assuming prefixed reduction factors of the most critical response parameters in current conditions, which are evaluated by means of a conventional elastic finite element analysis. Simple formulas relating the reduction factors to the equivalent viscous damping ratio of the dissipaters, ξeq, are proposed. These formulas allow calculating the ξeq values that guarantee the achievement of target factors. Finally, the energy dissipation capacity of the devices is deduced from ξeq, finalizing their sizing process. A detailed description of the procedure is presented in the article, by distinguishing the cases where the prevailing structural deficiencies are represented by poor strength of the constituting members, from the cases having excessive horizontal displacements. A demonstrative application to the retrofit design of a reinforced concrete gym building is then offered to explicate the steps of the sizing criterion in practice, as well as to evaluate the enhancement of seismic response capacities generated by the installation of the dissipative system.

scholarly journals Seismic Material Properties of Reinforced Concrete and Steel Casing Composite Concrete in Elevated Pile-Group Foundation

2015 ◽  
Vol 22 (s1) ◽  
pp. 141-148 ◽  
Author(s):  
Mi Zhou ◽  
Wancheng Yuan ◽  
Yue Zhang
Keyword(s):  
Reinforced Concrete ◽  
Seismic Performance ◽  
Damping Ratio ◽  
Pile Group ◽  
Ocean Engineering ◽  
Static Loads ◽  
Equivalent Viscous Damping ◽  
Static Tests ◽  
Equivalent Viscous Damping Ratio ◽  
Positive Effect

Abstract The paper focuses on the material mechanics properties of reinforced concrete and steel casing composite concrete under pseudo-static loads and their application in structure. Although elevated pile-group foundation is widely used in bridge, port and ocean engineering, the seismic performance of this type of foundation still need further study. Four scale-specimens of the elevated pile-group foundation were manufactured by these two kinds of concrete and seismic performance characteristic of each specimen were compared. Meanwhile, the special soil box was designed and built to consider soil-pile-superstructure interaction. According to the test result, the peak strength of strengthening specimens is about 1.77 times of the others and the ultimate displacement is 1.66 times of the RC specimens. Additionally, the dissipated hysteric energy capability of strengthening specimens is more than 2.15 times of the others as the equivalent viscous damping ratio is reduced by 50%. The pinching effect of first two specimens is more obvious than latter two specimens and the hysteretic loops of reinforced specimens are more plumpness. The pseudo-static tests also provided the data to quantitatively assessment the positive effect of steel casing composite concrete in aseismatic design of bridge.

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